1. Field of the Invention
The present disclosure generally relates to active material actuation and methods of compensating for voltage variation during the same. More particularly, the disclosure presents an equivalent power method of reducing the ill-effects of rapid voltage variation during active material actuation.
2. Discussion of Prior Art
Active material actuators offer many advantages over their electro-mechanical counterparts, including less noise (both with respect to acoustic and EMF), weight, energy consumption, and complexity, but typically require that a set of preconditions be met in order to ensure consistent performance. One precondition is the need to stabilize voltage or reduce the effects of rapid voltage variation. In an automotive setting, for example, it is appreciated that charging systems and batteries often produce varying voltages from cycle to cycle due to temperature variation, the changing age/life cycle of the voltage source, or other characteristics inherent to the circuit; moreover, voltage variations are also experienced intra-cycle due to occurrences such as engine start-up, verification requirements, etc. Where the controller is programmed to produce the same output irrespective of the real voltage, it is further appreciated that the timing and/or stroke of the actuator may be caused to consequentially vary; and as a result, a driven member or otherwise resultant action to be imprecisely translated or insufficiently produced.
Conventional mechanisms and circuit implements, such as voltage regulators, have been developed to maintain a generally constant voltage; however, these mechanisms/implements are not always practical, require additional parts, and may, therefore, result in substantial increases in complexity and costs. Among these, proportional-integral-derivative (PID) controllers have traditionally been used to account for such variations through the P and D parameters (constant or extracted from a look-up table of voltage and/or temperature), and the I parameter accumulated over time; however, these measures also present concerns. For example, look-up tables introduce discontinuity and reduce system robustness, while time delays due to integration may produce undesired performance.